1. Field of the Invention
The present invention is directed to a dry ash handling system for a municipal waste incinerator that cools ash to room temperature for easy handling and, more particularly, to a system that collects ash in a car in a sealed tunnel, allows maximum burn-out of the waste to occur and water-spray cools the ash to a safe handling temperature while in the sealed tunnel before transporting the sealed car to a landfill.
2. Description of the Related Art
Municipal solid waste incineration systems such as illustrated in FIG. 1, burn waste dumped in chute 10 in a rotary combustor 12 such as an O'Connor combustor described in detail in U.S. Pat. Nos. 3,822,651 and 4,066,024. Part of the burned waste leaves the O'Connor combustor as fly ash which travels up a an after burner/gas cleaning chamber 14 and is collected in a fly ash collection system. Bottom ash, including partially burned embers, fall out of the combustor 12 into an ash burning and collection hopper 16 which includes a water cooled stairway grate 18 that allows large embers more time to complete burn-out as they roll down the stairway 18. The stairway 18 includes air injection ports which force air against the large embers and attempts to complete burn-out by holding the larger pieces in the chamber 14 for an additional time. The ashes then fall into a quenching tank 20 which includes a conveyor 22 which carries the wet ash to an ash car 24. The water serves two functions: (1) it quenches the sometimes still smoldering ash, and (2) it forms an air seal between the ash pit and the combustor 12 which operates at a slightly negative pressure. Incineration systems that include a conveyor 22 are frequently taken out of service because large objects get caught in the drag conveyor flights, breaking a drag chain, causing the conveyor 22 to grind to a halt. The system, in such a situation, will be out of service for at least eight hours, the time required to cool down and then reheat the combustor 12. The water from tank 12, before discharge back into the environment, must be treated. The full ash car 24, loaded with wet ash, is carried to a landfill and emptied. Since waste carriers charge by the pound for disposal, the wet ash is much more expensive to discard than would be the ash if it were dry.
Dry ash handling systems have been produced that replace the water tank 20 and stairway 18 with a slowly moving conveyor at the bottom of the combustor 12. The conveyor is located approximately four feet from the bottom edge of the combustor 12 and moves at a rate which allows approximately one foot of dry ash to be deposited on the conveyor. The conveyor is a grate type conveyor that allows air to be injected into the ash in an attempt to complete combustion of larger embers. However, considerable dusting and scattering of the ash occurs in such systems and at times, burn-out of the ash is incomplete, resulting in smoldering ash being carried to the landfill.